1. Field of the Invention
The present invention relates to a switching regulator comprising an electronic switch and comprising a differential amplifier whose inputs are supplied with a quantity dependent on an actual value and with a reference value, and comprising a comparator whose inputs are connected to the output of the differential amplifier and to the output of a comparison quantity generator, whereby the comparison quantity generator emits a periodic comparison quantity having a prescribed chronological progression and the electronic switch can be periodically switched on at prescribed on-times with the assistance of a clock generator and can be respectively switched off at a time defined with the assistance of the comparator.
2. Description of the Prior Art
A switching regulator of the type generally set forth above is already known from U.S. Pat. No. 3,377,546, and is fully incorporated herein by this reference.
In a series arm, the known switching regulator contains a switching transistor as a final control element and a control circuit comprising a clock generator, whereby a rectangular control voltage having a constant period and a variable pulse duty factor is generated by super position of a triangular auxiliary voltage with a test voltage. In order to increase the control range of the switching regulator, i.e. the range of adjustment of the pulse duty factor, a trigger circuit generates a rectangular control voltage having high edge steepness (short rise time) which assures a fast switching of the transistor. The working range extends from the one limiting position to the other. The transistor can also be continuously conductive or continuously inhibited.
Given the usual application of a switching regulator for voltage regulation, however, it is not necessary to supply a feed voltage that is continuously variable between a maximum value and zero because either a constant voltage is to be supplied given a finite load resistor or the control voltage value zero need only be reached given the value zero of the load resistor with a short circuit current that is usually equal to or greater than the nominal current.
Investigations within the scope of the present invention have shown, however, that difficulties can arise given a switching regulator which employs a triangular current as a comparison voltage in that a specific constant change of the regulator voltage produces changes that are considerably greater percentage-wise at a low keying degree than at high keying values and that problems with respect to the stability thereof can thereby particularly derive when the gain of the regulating comparator is fixed in the region of high degrees of keying in accordance with the required accuracy.